Vehicle travel control method and travel control device

1. A travel control method for a vehicle, comprising: when, during autonomous travel control of a subject vehicle, a road section including at least one of a curve and a narrow road is present ahead of the subject vehicle and another vehicle is traveling in an adjacent lane to a traveling lane for the subject vehicle and ahead of the subject vehicle, estimating a position at which the subject vehicle passes the other vehicle, on a basis of a traveling speed of the subject vehicle, a traveling speed of the other vehicle, and an inter-vehicle distance between the subject vehicle and the other vehicle; when the position is located at a position farther from the subject vehicle than a starting point of the road section, determining that the subject vehicle cannot pass the other vehicle before the road section and executing inter-vehicle distance control in which the subject vehicle is controlled to travel with an inter-vehicle distance that is set such that the subject vehicle and the other vehicle do not travel side by side when the subject vehicle travels in the road section; and when the position is located at a position nearer to the subject vehicle than the starting point of the road section, determining that the subject vehicle can pass the other vehicle before the road section and executing the autonomous travel control in which the subject vehicle is controlled to pass the other vehicle.

2. The travel control method for a vehicle according to claim 1 , comprising: when a preceding vehicle traveling ahead in the traveling lane for the subject vehicle is present, determining whether or not the subject vehicle can pass the other vehicle before the road section while maintaining at least a current inter-vehicle distance from the preceding vehicle, on a basis of the traveling speed of the subject vehicle, a traveling speed of the preceding vehicle, an inter-vehicle distance between the subject vehicle and the preceding vehicle, and the estimated position at which the subject vehicle passes the other vehicle; and when a determination is made that the subject vehicle can pass the other vehicle, executing the autonomous travel control in which the subject vehicle is controlled to pass the other vehicle before the road section while maintaining the current inter-vehicle distance from the preceding vehicle.

3. The travel control method for a vehicle according to claim 2 , comprising: when a determination is made that the subject vehicle cannot pass the other vehicle, setting the inter-vehicle distance from the preceding vehicle to a shorter value than the current inter-vehicle distance thereby to determine whether or not the subject vehicle can pass the other vehicle before the road section; and when a determination is made that the subject vehicle can pass the other vehicle, setting the inter-vehicle distance from the preceding vehicle to the shorter value and executing the autonomous travel control in which the subject vehicle is controlled to pass the other vehicle before the road section.

4. The travel control method for a vehicle according to claim 1 , comprising: acquiring a curvature radius of a road located ahead of the subject vehicle; determining that the road located ahead is a curve included in the road section when the curvature radius is less than a curvature radius threshold; detecting a variation amount in a lateral position of the other vehicle during a certain period; and when the variation amount in the lateral position is a predetermined value or more, setting the curvature radius threshold to a larger value than that when the variation amount in the lateral position is less than the predetermined value.

5. The travel control method for a vehicle according to claim 1 , comprising: acquiring a road width of a road located ahead of the subject vehicle; determining that the road located ahead of the subject vehicle is a narrow road included in the road section when the road width is less than a narrow road threshold; detecting a ratio of a vehicle width of the other vehicle to the road width; and when the ratio is a predetermined value or more, setting the narrow road threshold to a larger value than that when the ratio is less than the predetermined value.

6. A travel control method for a vehicle, comprising: when, during autonomous travel control of a subject vehicle, a road section including at least one of a curve and a narrow road is present ahead of the subject vehicle, another vehicle is traveling in an adjacent lane to a traveling lane for the subject vehicle and ahead of the subject vehicle, and a preceding vehicle traveling ahead in the traveling lane for the subject vehicle is present, estimating a position at which the subject vehicle passes the other vehicle, on a basis of a traveling speed of the subject vehicle, a traveling speed of the other vehicle, and an inter-vehicle distance between the subject vehicle and the other vehicle; and determining whether or not the subject vehicle can pass the other vehicle before the road section while maintaining at least a current inter-vehicle distance from the preceding vehicle, on a basis of the traveling speed of the subject vehicle, a traveling speed of the preceding vehicle, an inter-vehicle distance between the subject vehicle and the preceding vehicle, and the estimated position at which the subject vehicle passes the other vehicle; and when the position at which the subject vehicle passes the other vehicle is located at a position nearer to the subject vehicle than a starting point of the road section and a determination is made that the subject vehicle can pass the other vehicle before the road section while maintaining at least the current inter-vehicle distance from the preceding vehicle, executing the autonomous travel control in which the subject vehicle is controlled to pass the other vehicle before the road section while maintaining the current inter-vehicle distance from the preceding vehicle; and canceling inter-vehicle distance control in which the subject vehicle is controlled to travel with an inter-vehicle distance that is set such that the subject vehicle and the other vehicle do not travel side by side when the subject vehicle travels in the road section.

7. The travel control method for a vehicle according to claim 6 , comprising: when a determination is made that the subject vehicle cannot pass the other vehicle, setting the inter-vehicle distance from the preceding vehicle to a shorter value than the current inter-vehicle distance thereby to determine whether or not the subject vehicle can pass the other vehicle before the road section; and when a determination is made that the subject vehicle can pass the other vehicle, setting the inter-vehicle distance from the preceding vehicle to the shorter value and executing the autonomous travel control in which the subject vehicle is controlled to pass the other vehicle before the road section.

8. A travel control method for a vehicle wherein, when, during autonomous travel control of a subject vehicle, a road section including a curve is present ahead of the subject vehicle and another vehicle is traveling in an adjacent lane to a traveling lane for the subject vehicle, inter-vehicle distance control is executed in which the subject vehicle is controlled to travel with an inter-vehicle distance that is set such that the subject vehicle and the other vehicle do not travel side by side when the subject vehicle travels in the road section, the travel control method for a vehicle comprising: acquiring a curvature radius of a road located ahead of the subject vehicle; determining that the road located ahead is a curve included in the road section when the curvature radius is less than a curvature radius threshold; detecting a variation amount in a lateral position of the other vehicle during a certain period; and when the variation amount in the lateral position is a predetermined value or more, setting the curvature radius threshold to a larger value than that when the variation amount in the lateral position is less than the predetermined value.

9. A travel control method for a vehicle wherein, when, during autonomous travel control of a subject vehicle, a road section including a narrow road is present ahead of the subject vehicle and another vehicle is traveling in an adjacent lane to a traveling lane for the subject vehicle, inter-vehicle distance control is executed in which the subject vehicle is controlled to travel with an inter-vehicle distance that is set such that the subject vehicle and the other vehicle do not travel side by side when the subject vehicle travels in the road section, the travel control method for a vehicle comprising: acquiring a road width of a road located ahead of the subject vehicle; determining that the road located ahead is a narrow road included in the road section when the road width is less than a narrow road threshold; detecting a ratio of a vehicle width of the other vehicle to the road width; and when the ratio is a predetermined value or more, setting the narrow road threshold to a larger value than that when the ratio is less than the predetermined value.

10. A travel control apparatus for a vehicle, comprising a controller configured to control travel of a subject vehicle in an autonomous manner, the controller being further configured to: when, during autonomous travel control of the subject vehicle, a road section including at least one of a curve and a narrow road is present ahead of the subject vehicle and another vehicle is traveling in an adjacent lane to a traveling lane for the subject vehicle and ahead of the subject vehicle, estimate a position at which the subject vehicle passes the other vehicle, on a basis of a traveling speed of the subject vehicle, a traveling speed of the other vehicle, and an inter-vehicle distance between the subject vehicle and the other vehicle; when the position is located at a position farther from the subject vehicle than a starting point of the road section, determine that the subject vehicle cannot pass the other vehicle before the road section and execute inter-vehicle distance control in which the subject vehicle is controlled to travel with an inter-vehicle distance that is set such that the subject vehicle and the other vehicle do not travel side by side when the subject vehicle travels in the road section; and when the position is located at a position nearer to the subject vehicle than the starting point of the road section, determine that the subject vehicle can pass the other vehicle before the road section and execute the autonomous travel control in which the subject vehicle is controlled to pass the other vehicle.